The invention relates to the production of aesthetic, permanent dental filling material that does not discolor and that counteracts the occurrence of secondary caries.
In tooth restorations, for aesthetic reasons, the goal is for the restored tooth region to be as effectively invisible as possible, so that it is visually indistinguishable from the natural tooth. Thus far, this has been done with composites, compomers and glass-ionomer cements, or with expensive porcelain or glass ceramic inlays, with variable results. However, such fillings have only inadequate durability and are quickly washed out. They also tend to discolor.
Bioactive glasses have already been known for long time and are described in summary fashion for instance by Larry L. Hench and John K. West in “Biological Applications of Bioactive Glasses”, Life Chemistry Reports 1996, Vol. 13, pages 187–241, or in “An Introduction to Bioceramics”, L. Hench and J. Wilson, Eds., World Scientific, New Jersey (1993). In contrast to conventional glasses, bioactive glasses are distinguished by being soluble in an aqueous medium and by forming a film of hydroxyl apatite on their surface. The most commonly used bioactive glasses are produced either as fusible glass, which then have a markedly lower proportion of SiO2 compared to normal window or bottle glasses, and a substantially higher proportion of sodium, or else are so-called sol-gel glasses, which in contrast to fusible glasses can contain a high proportion silicon oxide and a slight to completely absent amount of sodium.
The essential properties of bioactive glass are known to one skilled in the art and are described for instance in U.S. Pat. No. 5,074,916. According to this reference, bioactive glass differs from conventional lime-sodium-silicate glasses in that it binds living tissue.
Such bioactive glasses are used for instance for healing bone damage, and in particular as synthetic bone transplant material. They are moreover successfully used for healing chronic wounds, especially with diabetic ulcers and in pressure sores and bedsores in geriatrics. For instance, John E. Rectenwald, Sean Lee and Lyle L. Moldawer et al. (Infection and Immunity, submitted for publication) have been able to demonstrate that in the mouse, bioactive glass displays an inflammatory effect which by stimulation of interleukin-6 (IL-6) activity with simultaneous inhibition of the inflammation-stimulating cytokines TNF-alpha, IL-1-alpha and IL-10, as well as MPO (myeloperoxidase) (see also 19th Annual Meeting, Surgical Infection Society 1999, Apr. 28 to May 1, 1999).
From E. Allen, et al. (Departments of Microbiology in Periodontology, Eastman Dental Institute), it is also known that a bioactive glass 45-S-5, which can be procured from Bioglas® U.S. Biomaterials, Alachua, Fla. 32615, USA and which has an antibacterial action. Such an action cannot be achieved with normal glass beads (window glass).